Replace O2 Bank 1 Sensor 2 on 2008 Camry

Having observed a recurring engine check light with code P0137 on my 2008 Camry (2.4L 4 cylinder, 2AZ-FE) that finally became a solid "on", it seemed that it was time for a repair job. In this case, P0137 identifies the Bank 1 Sensor 2 oxygen sensor as having failed. This sensor is located in the exhaust system downstream of the catalytic converter. It is quite easily accessible with the car up on support ramps by sliding under the front of the vehicle (for a DIY on a garage floor).

Several things to be aware of for this relatively simple repair:

1. let the car (especially the exhaust system) cool down before this repair
2. the O2 sensor will likely be frozen in place due to rust
--the part must be "broken loose" before attempting removal
3. you need to know if your car complies with California emissions standards
--my car is California compliant. Don't assume your vehicle is *not* just because it was not manufactured in California. This may make a difference in the part used (and see #4, next).
4. there are (at least) two Denso replacement parts, 234-4627 and 234-4260 for the California emissions version of this 2008 Toyota Camry.
--the parts are identical except for the length of the connecting wire. 234-4260 has a 3" shorter wire and so I purchased it (although both will work) for my vehicle. It's a good idea to measure this length before settling on a part. Longer wire is OK, but getting wires that are too short means having to lengthen them (there are 4) or exchange the part. Both of these parts are available on Amazon for around $53 (as of 12/01/2014).
5. a special socket (22mm) may be needed for removal and/or for accurate installation torque.
--specified installation torque is 32 ft lb. The special socket(s) can be obtained from (among other places) auto parts stores such as Advance Auto Parts as a tool kit. If you get the sensor part at a local store that carries the tool kit (that you also buy), you will typically be able to return the kit for a full refund (so it really is becomes just a loaner kit). However, the sensor will cost more locally (typically around $90 plus tax) so a plan might be to just buy the tool kit (typically $35), get the sensor from Amazon (around $53) so that you get a nice tool to add to your tool box along with the needed part, all for about the same cost as purchasing the sensor itself locally. The tool kit can probably be purchased on Amazon as well... I didn't look into that.

Step by step replacement of the Bank 1 Sensor 2 oxygen sensor:

Step 1. Disconnect the vehicle battery.
Disconnect the ground side of the battery. If you want to ensure that all (or most) stored capacitive power is removed, step on the brake pedal for a few seconds after disconnecting the battery... but this is probably not necessary. Also, if you forget to disconnect the battery, it's probably not going to hurt anything as long as the ignition is off but removing electrical power is good practice before working on an electrical component. It also has the supplemental effect of clearing the engine check codes. This means that the check light will only turn on after the repair if some other failure exists or if the newly installed part is bad (unlikely).

Step 2. Disconnect the sensor plug.
A bit of pressure from a flat bladed screwdriver tip is all that's necessary here. When done correctly (there's a small serrated section on top of the female plug, that's where the pressure is needed), there will be a tiny "click" as the male plug is released and it can then be wriggled out of its receptacle.

Step 3. Breaking the sensor free.
The first thing to understand here (based on my experience anyway) is that WD-40 will *not* do this job well (if at all). I tried using WD-40 (because I had some sitting around) and the only thing I accomplished was partially rounding the edges of the 22mm mounting nut (this nut is an integrated part of the sensor). It simply would not come off, even with somewhat vigorous tapping of the part alternated with repeated application of WD-40 over a 1/2 hour period. The solution (and this was new to me) is to create a 50-50 mixture of ATF (automatic transmission fluid) and Acetone, mix it well in an applicator type container (e.g. an oiling can) and apply it liberally to the sensor nut area. Be sure to tap (I used a punch) the sensor to help it break free. I let this soak for 15 minutes, re-applied, tapped it some more and then waited for another 10 minutes before trying to unscrew the device. I was successful using a 10" pipe wrench with added leverage from a 1" diameter pipe slipped over its handle. However, I went to the pipe wrench approach only because I'd partially rounded the corners of the nut earlier (due to it not being loosened up by WD-40).

Step 4. Install the new sensor.
Each Denso part comes with a small tube of high temperature anti-seize compound. Be sure to apply this to the threads of the sensor before installing. This will make it easier to replace the sensor at a future date, should that ever become necessary. Screw the device in and then use a torque wrench to tighten it to 32 ft lbs. In my case, I no longer had the special socket tool kit so I used a regular 22mm wrench and tightened it about 3/4 of a turn beyond finger tight. Even so, I'm a big proponent of using the correct tightening torque, so I recommend using a torque wrench with the appropriate socket. Be careful here as you may have to do a manual adjustment on the torque amount if the wrench itself is not centered over the nut being tightened (meaning that you would be applying more torque than the setting on the wrench). Now connect the sensor plug and you're almost good to go.

Step 5. Re-connect the vehicle battery.
Re-attach the battery ground and start the car. The engine check light should be gone but if it re-appears, then the engine check code should be examined to followup on the new problem. If you don't have an OBDII compliant plug in (that will communicate with your smart phone, for example) to read (and/or reset) your engine check code(s), AutoZone is one place that will provide this service for free.

Summary
While it can be a bit irksome to get this sensor out it is only a 5 minute job after the removal is accomplished. If you try to get this sensor replaced at a Toyota service center or even most local shops, you will be paying $300 or more. As outlined here, you might (and I did) save $200+ by doing this yourself. Note, of course, that your results may vary ;-) but this is a very "doable" DIY job. Good luck!